Modern digital communications systems use sophisticated modulation and coding approaches to combat severe physical-layer distortions and still deliver high-throughput, low error-rate services to consumers. For example, Digital Television (DTV) in the U.S. uses signaling according to the ATSC A/53 Standard, (available in six parts at http://www.atsc.org/cms/index.php/standards/published-standards/) radiating an RF terrestrial broadcast that pushes 19.3 Mbps in a 6 MHz bandwidth through a VHF/UHF channel. Other global DTV standards are similar. This combination of throughput and propagation medium, coupled with increasing demand for services to mobile users, can impart significant dynamic distortions to the radiated broadcast, as witnessed by the consumer device.
Besides relying on advanced equalization strategies to remove the distortions to the received signal, DTV systems apply channel coding to the data prior to RF broadcast, so the DTV receiver necessarily employs a channel decoder to recover the user data—audio and video. This decoder usually uses a nested combination of forward error correction (FEC) techniques to drive the error rate down to imperceptible levels, usually O(10−6) BER, including Reed-Solomon and Trellis decoder, or Low Density Parity Check and BCH decoder. Implicit in the implementation of these FEC decoder algorithms is that the number of samples per frame, as defined by the specific protocol, be correct; that is, if the number of samples per frame is not what is expected by the FEC, the result is usually a catastrophic failure with lost, unrecoverable data.
Recent field measurements confirm the existence of RF propagation channels with severe dynamic multipath, so much as to cause cycle slips in timing recovery circuitry, or changes in system data delays, producing framed data to FEC decoders with inconsistent numbers of samples per frame in prior art receiver designs. These prior art receiver designs catastrophically fail in these cases.